The phrase "almost essential to" is correct and usable in written English.
It can be used to indicate that something is very important or necessary, but not absolutely required.
Example: "In today's digital age, having a strong online presence is almost essential to the success of any business."
Alternatives: "nearly crucial to" or "practically vital to".
imprimatur has become almost essential to the authority's survival.
The salsa is almost essential to create a perfect balance, but if you don't have time to make it, serve the nests with a lemon wedge instead, though it won't be the same.
At Madison Square Garden on Tuesday night — his first headlining show there, and a sellout — he teased the crowd with flashes of direct emotional manipulation, the sort adults would blanch at but is almost essential to ensnare their children.
Therefore, it becomes almost essential to identify and exclude data contaminated by local effects or connected with some large-scale systems.
In order to increase the son's advantage, families began to increase household savings for future marriage, to the extent that it became almost essential to prepare a house for the son's marriage (Wei and Zhang 2011).
It is also almost essential to have at least some direct (X-ray or NMR) structural information on the complexes in question if one is to try to infer structural changes from changes in cleavage patterns.
In every branch of science this preliminary search for regularities is an almost essential background to serious quantitative work, and in what follows it will be taken for granted as having been carried out.
It is essential to be a Party member if one wishes to become a Minister, almost essential for election to the assemblies, and essential in an army officer and among diplomats.
But the definition of war crime became almost as essential to my work in Kosovo as my pen and notebook or my tape recorder.
The Mail on Sunday's Craig Brown went further, acclaiming the book as "an unfussy and clear-headed study of the making of a poet, and. . . a gentle reminder that poetry can be almost as essential to the human spirit as breathing".
Michigan is almost essential for a Democrat to win; Florida is less central to the Democratic calculus, although polls suggest that Mrs. Clinton is ahead of Senator John McCain there now (who knows if that would be the case in November, but it's a tempting bit of agitprop to toss out there).
